Conventionally, as a condenser for use in a refrigeration cycle of car air-conditioners, a heat exchanger 50 as shown in FIGS. 16 and 17 is widely employed.
This heat exchanger 50 includes a pair of vertically disposed headers 52 and 52, a plurality of heat exchanger tubes 53 disposed in parallel each other with the opposite ends communicated with the headers 52 and 52, fins 54 disposed between the adjacent tubes 53 and at the outside of the outermost tube 53 and side plates 55 disposed at the outside of the outermost fin 54. The heat exchanger tubes 53 are grouped into a plurality of passes C1 to C3 by partitioning members 56 provided in the headers 52 and 52. A gaseous refrigerant introduced via the refrigerant inlet 57 provided at the upper portion of one of the headers 52 passes through each of the passes C1 to C3 in turn, and is condensed by exchanging heat with the ambient air while passing through the passes. The condensed refrigerant flows out through the refrigerant outlet 58 provided at the lower portion of the other header 52.
As a tube 53 used for such a heat exchanger 50, an aluminum extruded tube of a flat shape having a thickness smaller than a width and a plurality of refrigerant flow passages 53a each having a rectangular cross-sectional shape and extending in the tube longitudinal direction is widely used.
The aforementioned heat exchanger 50 is usually installed in a vehicle such as a car or a truck. In recent years, such a vehicle is required to be small in size and light in weight for the purpose of increasing the fuel economy, decreasing the harmful emission gas (CO2, NOx), decreasing the amount of refrigerant. Accordingly, all of the automobile parts are also required to be high in performance as well as small in size and light in weight. This requirement is also applied to the heat exchanger 50 without exception.
In order to decrease the weight of the heat exchanger tube 53, it is considered to decrease the tube height or the thickness of the peripheral wall of the tube 53.
However, the passage cross-sectional area of the refrigerant flow passage 53a decreases as the tube height decreases, causing increased passage flow resistance and increased pressure loss, which in turn may sometimes cause deterioration of the condenser performance.
Further, if the thickness of the exterior peripheral wall of the tube 53 is simply formed into a thin wall, the pressure resistance deteriorates and it becomes difficult to form an enough sacrifice corrosion resistance layer, which in turn causes deterioration of corrosion resistance.
The present invention aims to solve the aforementioned prior art problems and provide a heat exchanger tube and a heat exchanger capable of improving the heat exchanging performance while decreasing the size and weight.
Another objects of the present invention will be apparent from the following explanation.